Emotion dysregulation is thought to be a core mechanism underlying many medical and psychiatric disorders. In particular, emotion dysregulation is believed to play a crucial role in physical and emotional responses to pain. A growing body of basic research is beginning to illuminate the neural correlates and behavioral sequelae of emotion dysregulation and perception of pain. Concurrently, a growing body of clinical research supports the efficacy of selected psychosocial interventions for pain. However, little is known about how these treatments modulate emotional reactivity to pain. The proposed study will directly address this knowledge gap by examining how two, distinct psychosocial treatment modalities-Cognitive- Behavioral Therapy (CBT) and Mindfulness-Based Stress Reduction (MBSR)-impact two specific forms of emotion regulation-cognitive regulation (CR) and attention regulation (AR)-in patients with CLBP. Back pain affects up to 85% of people over their lives; up to 5% of all adults experience severe and debilitating effects of CLBP. CLBP is associated with a huge disease burden: it has a high rate of recurrence and is highly comorbid with psychiatric disorders, including major depression (MOD), substance abuse, and anxiety disorders. Although CLBP is a major cause of functional disability and suffering, how psychosocial treatments reduce that suffering is not well understood. Our overall approach is to use behavioral and neural measures of emotion regulation in the context of an RCT to examine the differential impacts of CBT versus MBSR on pain symptoms and well-being in patients with CLBP (Aim 1), to differential changes in CR and AR related to CBT versus MBSR (Aim 2), and to determine whether CR and AR mediate treatment outcome (Aim 3). The broad, long-term objective of this translational research program is to provide an empirical basis for refining and/or integrating specific components of CBT and MBSR for CLBP and strengthen our understanding of the role specific emotion regulation processes play in CLBP, as well as other medical and psychiatric disorders.